# Relationship history for MSHA mine 3608621

Current hierarchy: **Tammy L  Norton → Norton Stone Company → Norton Stone Company**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Norton'S Stone Company → Norton Stone Company; 1997-03-01 to 2009-02-17; source msha-controller-operator-history
- **controller_controls_mine:** Norman  Norton → Norton Stone Company; 1997-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Norman  Norton → Norton'S Stone Company; 1997-03-01 to 2009-02-17; source msha-controller-operator-history
- **controller_controls_mine:** Tammy L  Norton → Norton Stone Company; 2003-01-08 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Norton Stone Company → Norton Stone Company; 2009-02-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Tammy L  Norton → Norton Stone Company; 2009-02-18 to current/open; source msha-controller-operator-history